Process for the preparation of polyolefin/acrylonitrile coploymers and polyolefin/acrylic acid or substituted acrylic acid/acrylonitrile terpolymers

ABSTRACT

Terpolymers of polyolefin/acrylic acid or substituted acrylic acid/acrylonitrile are prepared by combining a polyolefin/acrylic acid or substituted acrylic acid copolymer with at least one dinitrile to form a mixture and reacting the mixture at a temperature of at least 200° C. for a time sufficient to form the terpolymer. Copolymers of polyolefin/acrylonitrile are obtained when the reaction is carried to completion. The total reaction masses obtained comprising terpolymer or copolymer, cyclic imide, solvent, when used and any unreacted dinitrile find use as pour point depressants in heavy hydrocarbon oils.

BACKGROUND OF THE INVENTION

It is known that polyethylene/acrylonitrile copolymer is a very effective pour point depressant for a range of crude oils. While polyethylene/acrylonitrile copolymer shows good pour point depressant performance, the problem has been with the manufacture of the copolymer. Until now, there has been no high yield low cost convenient one step route to the polyethylene acrylonitrile copolymer.

Polyethylene/acrylonitrile copolymer can be made by the copolymerization of ethylene and acrylonitrile. However the reaction conditions are extreme and acrylonitrile itself is relatively toxic. For example, in Germany, polyethylene/acrylonitrile copolymer has been made directly from the monomers ethylene and acrylonitrile at a temperature of 230° C. and 27,000 pounds per square inch pressure.

It would be desirable to provide a process for the manufacture of polyethylene acrylonitrile copolymer which could be carried out in a single step at atmospheric pressure or low pressures.

PRIOR ART

U.S. Pat. No. 2,377,795 to Loder discloses the preparation of adiponitrile by reaction of acetonitrile and adipic acid at temperatures between 225° C. and 300° C. and pressures from 50 atmospheres to about 500 atmospheres.

U.S. Pat. No. 3,841,850 to Aaron et al discloses pour point depressant copolymers of 82 to 90 mole percent ethylene with certain substituted ethylenes of 3 to 40 carbon atoms which have less than 18 carbon atoms in any linear side chain. Acrylic acid is disclosed as on of the substituted ethylenes. The pour point depressant copolymers are prepared at temperatures between 40° C. and 300° C. and pressures between 900 and 40,000 psig.

U.S. Pat. No. 4,926,582 to Motz et al discloses use of Oil soluble ethylene/acrylonitrile copolymers or terpolymers as pour point depressants. The ethylene/ acrylonitrile copolymers are prepared by polymerization of ethylene and acrylonitrile or by reacting acrylic acid with ethylene and pyrolyzing with ammonia to obtain the copolymer.

"Nitrile Synthesis Via the Acid-Nitrile Exchange Reaction", by David A. Klein, J. Org. Chem., Vol. 36, No. 20, 1971 pages 3050-3051, discloses a process for making nitriles in high yields by reacting carboxylic acids with short chain dinitriles (specifically, succinonitrile, glutaronitrile, and alpha methylglutaronitrile). The reference states that the reaction is driven to completion since the cyano acid formed as a by-product undergoes an internal cyclic imide formation, removing it from the equilibrium. The reaction is carried out at 150° C. to 300° C. without the use of pressure equipment and may be catalyzed by the addition of a small amount of acid catalysts such as sulfonic, sulfuric or phosphoric acids or their various salts.

THE INVENTION

In carrying out the process of the invention, a copolymer of an olefin and an acrylic acid or substituted acrylic acid is reacted with at least on dinitrile having the formula NC--C_(n) --CN where n=2 to 4 and C is branched or straight chain alkyl at a temperature of at least 200° C. for a time sufficient to form polyolefin/acrylonitrile copolymer.

In one aspect of the invention, where the reaction is not taken to completion, a polyolefin/acrylic acid or substituted acrylic acid/acrylonitrile terpolymer is formed.

The reaction may be carried out in the presence of an acid catalyst. The reaction may also be carried out in a high boiling point aromatic solvent.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a graph of crude oil pour point versus pour point depressant concentration of several pour point depressants in the crude oil.

DETAILED DESCRIPTION OF THE INVENTION

In carrying out the process of the invention, the reactants are placed in a suitable reaction vessel, heated to reaction temperature and held at that temperature for a sufficient time period to convert the reactants to the desired copolymer or terpolymer. The polyolefin portion of the polyolefin/acrylic acid or substituted acrylic acid copolymer feed to the reaction is formed from monomers selected from the group consisting of C₂ to C₂₀ alpha olefins and styrene and styrene derivatives having the formula: ##STR1## where R=CH₃, C₂ H₅, C₃ H₈, C₄ H₉, Cl, Br, COCH₃ and OCH₃

Examples of suitable monomers include ethylene, propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-docosene, styrene, p-methylstyrene, p-tertbutyl styrene, butadiene and isoprene.

The acid portion of the copolymer reactant is formed from acids selected from the group having the formula: ##STR2## where R=H, phenyl, C₁ to C₅ alkyl

Suitable examples of these acids include acrylic acid, methacrylic acid, 3,3-dimethylacrylic acid, 3,3-dimethylmethacrylic acid, crotonic acid, and cinnamic acid.

The copolymers may vary over a wide range of molecular weight, from as low as 2000 or 3000 to as high as 200,000 or more. Usually the molecular weight will vary from about 15,000 to about 100,000, with better pour point depressant products being obtained with the lower molecular weight copolymers.

The polyolefin/acrylic acid or substituted acrylic acid copolymer will usually contain from about 10 to about 25 weight percent of the acid depending on the composition of the copolymer. With a copolymer of polyethylene and acrylic acid, the optimum weight percent of acid in the copolymer is usually about 20 percent to provide the most effective pour point depressant product.

In the process of the reaction of the copolymer with a dinitrile to form the acrylonitrile copolymer or terpolymer, a cyano acid is formed as a by-product of the reaction. This cyano acid undergoes an internal cyclic imide formation which removes it from the equilibrium, thus driving the reaction to completion. The dinitriles which are used in the process invention and form such acids have the formula

    NC--C.sub.n --CN

where n=2 to 4 and C is branched or straight chain alkyl.

Examples of such dinitriles include glutaronitrile, 2-methylglutaronitrile, succinonitrile and adiponitrile.

It is convenient to use the normally solid polyolefin/acrylonitrile copolymers as pour point depressants in the liquid state. For this reason, among others, the process of the invention is preferably carried out in a solvent to provide a product which can be used "as is", that is without the addition of a solvent. A solvent is also desirable since it serves to maintain the reaction mixture in a liquid state during the reaction, which facilitates contact of the reactants, and also aids in mixing the reactants. When a solvent is used in the process, the product obtained is usually liquid at ambient temperature at up to 10 percent polyolefin/acrylonitrile polymer solids. From 10 to 30 percent polymer solids the finished product ranges from a soft to a stiff gel which may readily be remelted with heat.

The solvents employed in the process are those which are inert to the reaction and have a boiling point above the reaction temperature. Preferred are aromatic solvents containing at least about 75 percent C₉ to C₁₅ aromatic hydrocarbons and more preferably from about C₁₀ to C₁₂ aromatic hydrocarbons. These solvents typically have a boiling point at atmospheric pressure above 250° C. Typical examples of suitable solvents include biphenyl, bibenzyl, phenanthrene and anthracene. If desired, a refinery stream high in aromatics such as ethylene cracker bottoms may also be used as the solvent.

While the process is preferably carried out at atmospheric pressure to avoid the use of pressure vessels, it is possible to use pressures somewhat above atmospheric if desired. At such pressures above atmospheric, the boiling point of other aromatic compounds is increased to a level above the reaction temperature. At such higher pressures e.g. up to about 300 psig other aromatic solvents such as toluene, xylene, ethylbenzene, cumene, paracymene, and naphthalene may be used in the process.

The solvent will usually comprise from about 7 to about 95 weight percent of the total reaction system, and more usually between about 85 and about 92 weight percent.

The process is carried out at a reaction temperature of at least 200° C., preferably at least 225° C. and more preferably at least 235° C. The time of reaction is sufficient to complete the reaction to obtain the desired polymer product. The time of reaction will usually range from about 20 to 60 hours with shorter times being required at the higher temperatures. When the starting copolymer is a polyethylene/acrylic acid copolymer, the temperature employed in the process to obtain a product with maximum pour point depressant properties is at least 235° C. and preferably from 235° C. to about 245° C. and with the reaction being carried out for a time period of 21 to 24 hours.

Although it is not necessary, the process may be carried out in the presence of an acid catalyst. When a catalyst is employed, the products obtained are the same as those resulting from the noncatalytic process. The catalytic reaction may be carried out with or without a solvent, however, a solvent is preferred for the reasons given previously. Usually the amount of catalyst used is very small ranging from as low as 0.1 to as high as 1.0 percent by weight of the total reaction system. Normally there is no need to remove the catalyst from the reaction products. However, if removal is desired or should become necessary, it may be effected by extraction of the reaction mass with aqueous caustic or the equivalent.

A variety of acid catalysts may be used in the process including mineral acids such as phosphoric acid, hydrochloric acid, phosphorous acid, fluorosulfonic acid and chlorosulfonic acid. Also useful are organic acids such as benzene sulfonic acid, methane sulfonic acid, p-toluene sulfonic acid, p(n-dodecyl-benzene sulfonic acid, alkyl sulfonic acids having the formula:

    R--SO.sub.3 H

where R=C₁ -C₁₂ alkyl groups and alkyl phosphonic acids having the formula: ##STR3## where R=C₁ -C₁₂ alkyl groups and other phosphonic acids, such as 1-hydroxyethylidene-1,1-diphosphonic acid, amino tri (methylene phosphonic acid) and ethylenediamine tetra (methylene phosphonic acid).

When a catalyst is employed in the process the process may be carried out at lower temperatures or for a shorter time period to obtain the desired products.

The process of the invention may be used to prepare polyolefin/acrylonitrile copolymers or terpolymers of polyolefins, acrylic acid or substituted acrylic acids and acrylonitrile. Usually the conversion of the polyolefin/acid copolymer will be at least 75 percent and more usually 85 to 95 percent under the reaction conditions described. The percent conversion is related to the time period over which the reaction is carried out, the amount of dinitrile present in the reaction mass, and the reaction temperature. When the reaction is carried out to completion, the resulting product is a polyolefin/acrylonitrile copolymer. If the reaction is not carried to completion, the product is a terpolymer of olefin, acrylic acid or substituted acrylic acid and acrylonitrile. The percentage of acrylic acid or substituted acrylic acid in the terpolymer product ma be varied by the temperature and time of the reaction or by limiting the amount of dinitrile used in the process. If the purpose of the reaction is to produce the polyolefin/acrylonitrile copolymer, at least a stoichiometric amount of the dinitrile (1:1 stoichiometric ratio) is required in the process and preferably the process is carried out with an excess of dinitrile up to 25 percent or more in excess of stoichiometric. If desired of course, larger amounts of the dinitrile may be used in the process.

The preferred reactants in the process are polyethylene/acrylic acid copolymer containing about 20 weight percent acrylic acid and alpha methylglutaronitrile. The co-product of this reaction is 3-methylglutarimide.

The reaction products of the process of the invention may be used as pour point depressants in various heavy hydrocarbon oils, including shale oils, crude oils, residua containing fuels and distillate fuels. Residua containing fuels are fuels comprising residua from the distillation of crude oil or shale or mixtures thereof. Flash distillate fuels are those fuels obtained by the flashed distillation at reduced pressure of residual oils. Although the reaction products may be used as pour point depressants in any crude oils, they are particularly effective with high pour point waxy crude oils. They find particular application in waxy crude oils obtained from areas such as India, Egypt and the British North Sea.

It has been found that the products of the process of the invention may be used "as is" without any treatment of the reaction mass. Thus, it is not necessary to separate out the copolymer or terpolymer product from the reaction mass. The entire reaction mass of copolymer or terpolymer, solvent, imide and any unreacted dinitrile may be used directly as a pour point depressant in heavy hydrocarbon oils. Usually it is also unnecessary to remove the acid catalyst from the reaction mass when such a catalyst is used because the amount of catalyst required is so small.

If removal of the copolymer or terpolymer product from the reaction mass is desired, it may be effected by extraction of the reaction mass with a suitable solvent. In one extraction procedure, methanol or acetone solvent is used in an amount equal to between 5:1 and 10:1 ratio based on the total reaction products. The reaction products ar added slowly to rapidly stirred solvent at ambient temperature. Solids precipitate quickly and are collected by filtration. The solids are then dried in a vacuum oven to provide the polymer product. If one precipitation is not sufficient, the polymer solids may be redissolved in an aromatic hydrocarbon solvent and the above process repeated.

The following examples are presented in illustration of the invention.

EXAMPLE 1

A number of runs were carried out at atmospheric pressure in which an ethylene/acrylic acid copolymer, a dinitrile and an aromatic solvent were introduced to a reaction flask. In each run stirring and heating were started after the ingredients had been charged to the flask. The temperature was raised to the desired reaction temperature over a period of 1 to 2 hours and was continued at that level for the desired reaction time period. The reaction mixture was then cooled and was used directly as a finished product. There was no attempt made to separate the polymer produced in the reaction from the imide, unreacted dinitrile, or from the catalyst in those runs in which a catalyst was employed. The various reaction conditions and the quantities of starting materials used are set forth in Table 1. This table also includes pour point depressant performance results in crude oil for each of the reaction masses obtained in the runs.

                                      TABLE 1                                      __________________________________________________________________________                           Reaction                                                                              Pour Point Depressant                             Run                                                                               EAA      Aromatic  Temp                                                                               Time                                                                              Performance                                       #  Polymer                                                                             Nitrile                                                                            Solvent                                                                             Catalyst                                                                            °C.                                                                         Hrs.                                                                              Results Pour Point °F.                     __________________________________________________________________________      1 20% AA                                                                              MGN 135 g                                                                               H.sub.3 PO.sub.4                                                                    230 24 PPM 100 250 // 25 50 75 100*                         15 g 50 g     1.0 g       Pour Pt. 50 40 // 65 60 50 45                      2 20% AA                                                                              MGN  90 g                                                                               H.sub.3 PO.sub.4                                                                    239 22 PPM 100 250 // 25 50 75 100*                         10 g 33 g     0.7 g       Pour Pt. 50 40 // 80 65 45 40                      3 20% AA                                                                              GN  135 g                                                                               H.sub.3 PO.sub.4                                                                    234 22 PPM 100 250 // 25 50 75 100*                         15 g  4.7 g   0.8 g       Pour Pt. 40 40 // 80 65 50 50                      4  --  MGN  90 g                                                                               H.sub.3 PO.sub.4                                                                    235 21 PPM 100 250                                               33.6     0.7 g       Pour Pt. 85 85                                     5 20% AA                                                                              MGN  90 g                                                                                --  239 22 PPM 50 100                                           10 g 33 g                 Pour Pt. 65 50                                     6 20% AA                                                                              SN   90 g                                                                               H.sub.3 PO.sub.4                                                                    240 21 PPM 50 100                                           10 g  2.4 g   0.5 g       Pour Pt. 75 65                                     7 20% AA                                                                              MGN  90 g                                                                                --  240 21 PPM 50 100                                           10 g 33 g                 Pour Pt. 65 55                                     8 20% AA                                                                              MGN  90 g                                                                                --  235 24 PPM 50 100 // 25 50 75 100*                          10 g 33 g                 Pour Pt. 75 55 // 70 55 50 45                      9 20% AA                                                                              MGN  90 g                                                                                --  242 23 PPM 50 100                                           10 g  3.6 g               Pour Pt. 60 55                                    10 20% AA                                                                              MGN  90 g                                                                                --  242 23 PPM 50 100                                           10 g  1.8 g               Pour Pt. 85 50                                    11 20% AA                                                                              MGN**                                                                               90 g                                                                                --  241 24 PPM 50 100                                           10 g 33 g                 Pour Pt. 85 55                                    12 20% AA                                                                              MGN  90 g                                                                                --  242 12 PPM 50 100                                           10 g  3.6 g               Pour Pt. 80 80                                    13 20% AA                                                                              MGN  90 g                                                                                --  243  6 PPM 50 100                                           10 g  3.6 g               Pour Pt. 85 80                                    14 20% AA                                                                              MGN 120 g                                                                                --  242 24 PPM 50 100                                           10 g  3.6 g               Pour Pt. 70 50                                    15 20% AA                                                                              MGN  90 g                                                                                --  243 24 PPM 50 100 // 50 100 // 25 50 75 100***              10 g  3.6 g               Pour Pt. 55 55 // 75 50 // 80 75 60 50            16 20% AA                                                                              MGN  90 g                                                                                --  241  3 PPM 50 100                                           10 g  3.6 g               Pour Pt. 80 80                                    17 20% AA                                                                              MGN  90 g                                                                                --  225 24 PPM 50 100 // 50 100*                                10 g  3.6 g               Pour Pt. 80 65 // 80 80                           18 15% AA                                                                              MGN 120 g                                                                                --  238 23 PPM 50 100 // 50 100*                                10 g  5 g                 Pour Pt. 85 75 // 80 75                           19 10% AA                                                                              MGN 120 g                                                                                --  242 24 PPM 50 100                                           10 g  5 g                 Pour Pt. 85 85                                    20 15% AA                                                                              MGN 120 g                                                                                --  240 24 PPM 50 100 // 50 100 // 25 50 75 100***              10 g  5 g                 Pour Pt. 85 75 // 80 65 // 80 80 80 60            21 10% AA                                                                              MGN 120 g                                                                                --  242 24 PPM 50 100                                           10 g  5 g                 Pour Pt. 85 85                                    22 20% AA                                                                              MGN 120 g                                                                                --  241 24 PPM 50 100 // 50 100 // 25 50 75 100***              10 g  5 g                 Pour Pt. 80 75 // 60 50 // 75 55 50 50            23 20% AA                                                                              MGN 120 g                                                                                --  239 24 PPM 50 100 // 50 100 // 25 50 75 100***              10 g  5 g                 Pour Pt. 80 75 // 55 55 // 70 65 50 50            24 20% AA                                                                              MGN 120 g                                                                                --  241 24 PPM 50 100 // 25 50 75 100*                          10 g  5 g                 Pour Pt. 55 40 // 65 50 50 45                     25 20% AA                                                                              MGN 480 g                                                                                --  241 43 PPM 50 100 // 15 30 45 60 75*                        40 g 20 g                 Pour Pt. 50 45 // 80 65 55 50 50                  26 20% AA                                                                              MGN 120 g                                                                                --  234 24 PPM 50 100                                           10 g  5 g                 Pour Pt. 55 50                                    27 20% AA                                                                              MGN 120 g                                                                                --  241 48 PPM 50 100                                           10 g 10 g                 Pour Pt. 50 45                                    28 20% AA                                                                              MGN 120 g                                                                                --  241 24 PPM 50 100                                           10 g 10 g                 Pour Pt. 60 50                                    29 20% AA                                                                              MGN 120 g                                                                               p-TSA                                                                               242 23 PPM 50 100                                           10 g  5 g     0.75 g      Pour Pt. 50 45                                    30 20% AA                                                                              MGN 120 g                                                                               MSA  242 24 PPM 50 100                                           10 g  5 g     0.5 g       Pour Pt. 60 45                                    31 20% AA                                                                              MGN 2016 g                                                                               --  241 24 PPM 50 100                                           168 g                                                                               84 g                 Pour Pt. 80 50                                    32 20% AA                                                                              MGN 2825 lbs.                                                                            --  250 24 PPM 50 100                                        ****                                                                              327 lbs.                                                                            171 lbs.             Pour Pt. 45 50                                    __________________________________________________________________________      Legend for Table 1                                                             MGN Alpha methylglutaronitrile                                                 EAA Polyethylene/Acrylic Acid Copolymer                                        AA Acrylic Acid                                                                SN Succinonitrile                                                              GN Glutaronitrile                                                              pTSA pToluene Sulfonic Acid                                                    MSA Methane Sulfonic Acid                                                      *Two groups of tests were carried out at different times                       **A different grade of MGN was used in this run                                ***Three groups of tests were carried out at different times                   ****Pilot Plant Run                                                      

The pour points of the reaction products were obtained in Bombay High South Crude having an API gravity of 38.8, a cloud point of 85°-88° F., a pour point of 85° F. and wax content of 11.6% at 0° C. and 19.0% at -30° C. The pour point of the crude without the addition of any reaction product was 80° to 85° F. As stated previously, no attempt was made to separate out copolymer or terpolymer from the reaction mass, nor was there any attempt to remove catalyst or any unreacted nitrile.

Acid catalysts were used in a number of the runs, i.e. Runs 1 to 4, 6, 29 and 30. With the exception of Run 4, the pour point depressant performance was good for the reaction masses of all of these runs. The reaction masses obtained without the use of a catalyst were also very effective pour point depressants, e.g. Runs 5, 7 to 9, 11,14, 15, 22 to 28, 31 and 32.

In most of the runs a minimum of 1:1 mole ratio of alphamethyl glutaronitrile to polyethylene/acrylic acid copolymer was employed. In a number of runs, an excess ranging from 1.4 to 14 mole ratio was used. When a substantially lesser amount of alphamethyl glutaronitrile is used in the reaction, the pour point depressant performance result is usually poor. This is illustrated by Run 10 where the ratio was 0.50 to 1.

Reaction temperatures generally varied from 238° C. to 242° C. One test (Run 17) was carried out at 225° C. and the pour point depressant results were poor. The majority of the tests were made using a copolymer containing 20% acrylic acid. In runs 18, 19 20 and 21 the copolymers contained 15%, 10%, 15% and 10% acrylic acid respectively. In each of these runs, the pour point depressant results were generally poor.

The reaction times employed usually were from 21 to 24 hours, however in a few runs higher reaction times were used. In three runs, 13, 14 and 17, substantially shorter reaction times were used. In each instance the pour point performance of the reaction mass was poor.

EXAMPLE 2

Two runs were carried out using the same procedure as in Example 1 in which a aromatic solvent was not used in the reaction of ethylene/acrylic acid copolymer and dinitrile. Instead, an excess of 2-methylglutarolnitrile was used, in a molar ratio of about 46 to 1. Thus the 2-methylglutaronitrile in effect acted as a solvent as well as reactant. Pertinent data relating to the two runs is contained in Table 2.

                                      TABLE 2                                      __________________________________________________________________________                                    Pour Point                                                                     Depressant                                      Run                                                                               EAA                  Temp                                                                               Time                                                                              Performance Results                             #  Polymer                                                                             Nitrile                                                                            Solvent                                                                             Catalyst                                                                              °C.                                                                         Hrs.                                                                              Pour Pt. °F.                             __________________________________________________________________________     1  20% AA                                                                              MGN Excess                                                                              --     250 18 PPM 100 250                                        10 g 166.2 g                                                                            MGN                Pour Pt. 40 35                                  2  20% AA                                                                              MGN Excess                                                                              85% H.sub.3 PO.sub.4                                                                  250 16 PPM* 100 250                                       10 g 166.2 g                                                                            MGN  1.1 g         Pour Pt. 50 45                                                                 PPM** 100 250                                                                  Pour Pt. 50 45                                  __________________________________________________________________________      *Amorphous                                                                     **Needles                                                                

A dark black reaction mass wa obtained in Run 1. This mass was cooled during which solids separated from the reaction mass; which solids were filtered to recover polymer product. The polymer product was dissolved in an aromatic solvent and then tested for pour point depressant properties in Bombay High South crude. It is noted from the table that the polymer product showed very good pour point depressant properties.

The reaction mass obtained in Run 2 was treated in a similar manner to isolate polymer solids. In this instance, two types of polymer solids were obtained, one was a crude amorphous type material and the other needlelike solids. Both of these solids were dissolved in aromatic solvents and tested for pour point depressant properties in Bombay High South crude. It is noted from the table that both polymer products provided good pour point depressant results.

EXAMPLE 3

A pour point depressant was prepared using the same procedure set forth in Example 1. 10.0 grams of polyethylene/acrylic acid copolymer containing 20% acrylic acid was reacted with 4.6 grams of alphamethylglutaronitrile in 90.0 grams of aromatic solvent at atmospheric pressure and a temperature of 242° C. for 24 hours. Pour point depressant performance was obtained for the entire reaction mass in Bombay High South crude. For comparison, two commercial pour point depressants were also tested in the sam crude. The results of the tests are shown in FIG. 1 in which pour point depressant No. 1 is the total reaction mass obtained by the process of the invention, and pour point depressants Nos. 2 and 3 are the commercial pour point depressant materials.

Satisfactory pour point performance is frequently determined in the range of 50° to 65° F. It is noted that in this range, the pour point performance of the reaction mass obtained by the process of the invention is substantially better than the commercial pour point depressants in terms of the amount of pour point depressant material required to obtain the desired pour point.

EXAMPLE 4

In several of the runs made in Example the reaction product was processed by solvent precipitation to separate out polymer products. The separated polymer was then analyzed to determine the percent conversion of carboxyl in the starting copolymer reactant. The methods of polymer separation and the percent carboxyl conversion are set forth in Table 3.

                  TABLE 3                                                          ______________________________________                                         Separated Polymer Solids                                                       Run #                     % Carboxyl                                           Table 1    Method of Separation                                                                          Conversion*                                          ______________________________________                                          1         M              85-90                                                 3         M and A        75-80                                                 5         M and A        85-90                                                 9         M and A        80-90                                                 9         3M             ˜90                                            10         M              35-50                                                15         M              90-95                                                15         3M              95-100                                              17         M              50-70                                                31         M              90-95                                                32         2M              95-100                                              ______________________________________                                          M  precipitation from large excess of methanol                                 A  precipitation from large excess of acetone                                  2M  two precipitation cycles with methanol                                     3M  three precipitation cycles with methanol                                   *  estimated conversion based on infrared spectrum analysis and acid           titration number.                                                        

It is noted that two runs 9 and 18 are included in the table. These illustrate the results obtained with two separate samples taken from Runs 9 and 18. It is further noted that the percent carboxyl conversion ranges from 35% to 100% which illustrates the production of terpolymers of varying carboxyl content and copolymers wherein the carboxyl conversion was 100%.

EXAMPLE 4

Several additional runs were carried out in which a variety of polyethylene/acrylic acid copolymers were used as the copolymer reactant. In each of the runs, 10 grams of the copolymer was reacted with 5 grams of 2-methylglutaronitrile in 120 grams of a aromatic solvent. The reaction was carried out at a temperature of 240° C. for a period of 24 hours. The total reaction mass after cooling was tested for pour point depression performance in Bombay High South crude. The results of the tests are set forth in Table 4.

                  TBLE 4                                                           ______________________________________                                                                    PPD Performance                                     Run # Wt % AA    Melt Index                                                                               Pour Point °F.                               ______________________________________                                         1     19         102       PPM      50   150                                                              Pour Point                                                                              55    50                                   2     19         316       PPM      50   150                                                              Pour Point                                                                              50    45                                   3     19         582       PPM      50   150                                                              Pour Point                                                                              45    35                                   4     25         276       PPM      50   150                                                              Pour Point                                                                              50    50                                   5     25         112       PPM      50   150                                                              Pour Point                                                                              65    60                                   6     20          80       PPM      50   150                                                              Pour Point                                                                              55    50                                   ______________________________________                                    

It is noted that the melt index of the polyethylene acrylic acid copolymer reactant ranged from 80 to 582. This corresponds nominally to a molecular weight range of about 100,000 to about 15,000. All of the copolymers over this wide range of molecular weight provided reaction masses having good pour point depressant properties, with the better results being obtained with the lower molecular weight copolymers.

While certain embodiments and details have been shown for the purpose of illustrating the present invention, it will be apparent to those skilled in the art that various changes and modifications may be made herein without departing from the spirit or scope of the invention. 

We claim:
 1. A pour point depressant composition comprising the total reaction mass obtained by combining a polyolefin/acrylic acid or substituted acrylic acid copolymer having a molecular weight of at least 2,000 with at least one nitrile selected from the group consisting of dinitriles having the formula NC--C_(n) --CN where n=2 to 4 and C is branched or straight chain alkyl, in the presence of a solvent inert with respect to the reaction, where the solvent boils above reaction temperature at the reaction pressure, to form a mixture and reacting the mixture at a temperature of at least 200° C. for a time sufficient to form a reaction product comprising polyolefin/acrylonitrile copolymer, solvent, cyclic imide and any unreacted dinitrile.
 2. A pour point depressant as described in claim 1 wherein the copolymer has a molecular weight of at least 15,000.
 3. A pour point depressant as described in claim 2 wherein the solvent comprises at least 70 weight percent of the reaction mixture.
 4. A pour point depressant composition comprising the total reaction mass obtained by combining a polyolefin/acrylic acid copolymer having a molecular weight of at least 2,000 with at least 1 nitrile selected from the group consisting of dinitriles having the formula NC--C_(n) --CN where n=2 to 4 and C is branched or straight chain alkyl where the dinitrile is present in at least stoichiometric ratio, in the presence of a solvent inert with respect to the reaction which solvent boils above reaction temperature at the reaction pressure to form a mixture and reacting the mixture at atmospheric pressure and a temperature of at least 200° C. for a time sufficient to form a reaction product comprising polyolefin/acrylonitrile copolymer, cyclic imide, solvent and any unreacted dinitrile.
 5. The composition of claim 4 in which the polyolefin portion of the copolymer is formed from monomers selected from the group consisting of C₂ to C₂₀ alpha olefins and styrene and styrene derivatives having the formula: ##STR4## where R=CH₃, C₂ H₅, C₃ H₈, Cl, Br, COCH₃ and OCH₃ and the acid portion of the copolymer is formed from acids selected from the group having the formula ##STR5## where R=H, phenyl, C₁ to C₅ alkyl.
 6. The composition of claim 4 wherein the reaction occurs at a temperature of at least 235° C.
 7. The composition of claim 4 wherein the reaction is catalyzed by an acid catalyst.
 8. The composition of claim 7 wherein the acid catalyst is selected from the group consisting of mineral acids selected from the group consisting of phosphoric acid, hydrochloric acid, phosphorous acid, fluorosulfonic acid and chlorosulfonic acid and organic acids selected from the group consisting of benzene sulfonic acid, methane sulfonic acid, p-toluenesulfonic acid, p(n-dodecylbenzene sulfonic acid, alkyl sulfonic acids having the formula:

    R--SO.sub.3 H

where R=C₁ -C₁₂ alkyl groups and alkyl phosphonic acids having the formula: ##STR6## where R=C₁ -C₁₂ alkyl groups 1-hydroxyethylidene-1,1-diphosphonic acid, amino tri (methylene phosphonic acid) and ethylenediamine tetra (methylene phosphonic acid).
 9. The composition of claim 4 wherein the polyethylene/acrylic acid or substituted acrylic acid copolymer contains at least 20% weight acrylic acid or substituted acrylic acid.
 10. The composition of claim 9 wherein the reaction time is at least 24 hours.
 11. A heavy hydrocarbon oil containing the reaction mass of claim
 4. 